Is possible to have hard water but water may be lacking calcium, or maybe has calcium, and lacking magnesium.Water hardness test's don't tell you which may be lacking.(local water report might)
I have plenty of calcium, and little to no magnesium in my water and so I decided to try adding a little Epsom salt (magnesium) when i dose other nutrient's and plant's that were doing poorly,improved.
Seachem's Equilibrium might also produce result's.
At first that was my line of thinking. But what got me confused is that I have been using the city water for the past 4 years on this tank. All of the crypts and plants were all thriving until this happen. Also only some of the crypts were affected. Usually I would see all or none or like one area of the tank. The affected crypts are all over the tank... not in a particular area.
Like wabisabi said, I really think AS has something to do with it.
I have dosed some calicium and GH booster last night. I will continue to monitor the crypts to see what happen next.